1. Field of the Invention
The present invention relates to a power storage device and a manufacturing method thereof.
2. Description of the Related Art
In recent years, lithium secondary batteries as power storage devices have been widely used as power supplies of consumer electrical devices such as game machines and information terminals typified by mobile phones and smartphones.
For such electrical devices, the need of power storage devices having not only long life and high capacity but also sheet-like shapes and flexibility for reductions in weight and size and a greater freedom for design of outer shapes has been increased. Flexible sheet-like power storage devices can be provided even for curved or bent portions and thin portions such as band portions of wristwatches, clothes, and thin electric alliances.
Lithium secondary batteries which are conventional nonaqueous secondary batteries each generally include positive electrodes and negative electrodes; the positive electrodes each include a positive electrode current collector made of sheet-like aluminum or the like and a positive electrode mix which includes a positive electrode active material capable of occluding and releasing lithium ions and which is applied to both surfaces of the positive electrode current collector, and the negative electrodes each include a negative electrode current collector made of sheet-like copper or the like and a negative electrode mix which includes a negative electrode active material capable of occluding and releasing lithium ions and which is applied to both surfaces of the negative electrode current collector. The positive electrodes and the negative electrodes are rolled with a separator interposed therebetween to form a rolled body, a positive electrode tab and a negative electrode tab are connected to given portions of the positive electrodes and the negative electrodes, and a nonaqueous electrolytic solution and the rolled body where the tabs are connected to the given portions of the positive electrode and the negative electrode are sealed in an exterior body with a certain shape such as a cylindrical shape, a square shape, or a coin shape. Although being flexible, the positive electrode, the separator, and the negative electrode have fixed forms and completely lose their flexibility such as capability of being bent freely, after the rolled body is formed and sealed in a container. Thus, the lithium secondary battery cannot have flexibility of being curved or bent and it is difficult to provide the lithium secondary battery for a curved or bent portion of an electrical device.
Therefore, for example, a solid secondary battery such as the solid secondary battery disclosed in Patent Document 1 has been actively researched. Such a solid secondary battery has a structure where an inorganic solid electrolyte or an organic solid electrolyte is substituted for a conventional nonaqueous electrolytic solution. Specifically, a positive electrode active material, a solid electrolyte, a negative electrode active material, and a negative electrode current collector are provided over a positive electrode current collector and the whole is made to be thin and have flexibility.